Which of the Following Is Possible in a Modified Cox,Ross,Rubinstein

Multiple Choice

Which of the following is possible in a modified Cox,Ross,Rubinstein binomial tree?

A) The interest rate and volatility can both be functions of time
B) The interest rate or the volatility can be a function of time, but not both
C) The interest rate can be a function of time but the volatility cannot
D) The interest rate and volatility must be constant